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What to expect for EGR back transducer/filter, gasket repair?


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20 replies to this topic

#1 subienewbie111

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Posted 18 January 2013 - 02:37 PM

Hello everyone,

I'm yet another person with an EGR/p0400 engine issue that I'm trying to find out more about.. disclaimer: I am not a car expert, so bear with me here.

Essentially, after well over 200,000 miles, things are getting pretty clogged up. Check engine light recently came on in my 96, 2.2L Legacy wagon. Fortunately, no noticeable driveability problems, pinging or other issues, likely due to the cold. My mileage seems to be slightly worse, but that might be the cold as well..but I do think this is related. I was told the car will pretty much drive fine, FOR NOW, while it's still cold, but that I would see problems as soon as it starts to warm up outside.

I was told over time my engine had "carboned up" and that the EGR back transducer (spelling??) is the cause. I would evidently need the back pressure filter and some gaskets replaced as well. This is going to run me nearly $600 (which does include an oil change, but still, YIKES). I'm going to get a second opinion, but has anyone else had a similar issue and had to replace the back transducer? Any thoughts on this?


(I apologize if there are several repeats on this topic - I know there are several threads about EGR and P0400 issues, but I have questions about cost of repair that might be slightly different, so I'm posting. If this is repeated too often feel free to delete and I apologize!)

#2 Fairtax4me

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Posted 18 January 2013 - 08:56 PM

Non-sense! This is a perfectly relevant question.
Non-sense! It probably isn't the BPT. Though it can be, it's more likely the EGR valve itself has clogged. And this is very easy to test without even removing the valve. First we need to identify the EGR valve. It's on the drivers side rear of the intake manifold. Has a metal cone shape with holes in the sides. Through the holes you can see a shaft in the middle and a rubber diaphragm.
Now to test it. Using a small crescent wrench (just large enough to fit the open end around the EGR shaft) push the diaphragm towards the rear of the car.
The shaft and diaphragm should move easily and should return to the rest position easily.
Now start the car and allow it to warm up enough to at least reach normal idle speed. Repeat the above test. If the EGR valve or piping leading to is clean, the engine should stall right away. Releasing the valve should return it to its rest position. If the engine does not stall, either the valve itself or the pipe leading to it or the port in the cylinder head is clogged with carbon and will need to be cleaned.

If the engine stalls while performing the above test this could mean the BPT is bad, or the Vacuum hose to the EGR valve is split. There are several hoses that go to the BPT and EGR valve, and a solenoid under the intake runner near the valve. Check the vacuum hoses for fit and connection.
To test the solenoid poke your head under the driver side dash and look for two green plugs with one wire each. They should be toward the center of the car. Plug them in and turn the key to ON. This puts the ECU in Test mode, which makes it cycle the radiator fans and all of the solenoids in about half second intervals. Put your finger on the EGR solenoid and feel for it to click on and off. Hook a vacuum hose to it if you can and blow through it. Air should flow and then stop coinciding with every other click (on, off) of the solenoid. If air flows through the solenoid at all times it should be replaced. If no air flows through the solenoid (none at all) it should be replaced. If the solenoid does not click it should be replaced.
If the solenoid checks out and all vacuum hoses are properly connected and the engine stalls when the EGR valve is opened at idle, replace the BPT. It's the black plastic thing clamped to the manifold right next to the EGR valve.
Picture of a Subaru EGR valve. Yours may not be exactly the same but it should be similar in appearance. BPT is the thing with the green sticker just above it. This view is looking forward from the back of the engine on the drivers side.
Posted Image

Also, Welcome to the board!

Edited by Fairtax4me, 18 January 2013 - 09:04 PM.


#3 1-3-2-4

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Posted 20 January 2013 - 06:41 PM

I've got the same code right now I think it might be the pipe that goes from the EGR to the head but until I can get it off I wont know, for some reason it's hard to get off the EGR end of it :-/

I'd have to try that test myself, and you can't miss the EGR or BPT, one thing I know is sometime when at idle after the car is nearing operating temp the RPMs go up and down like 100-200 and since my muffler is not on just yet you can really hear it, does not do it as much as if you drive and then stop at a light or whatever.. I cleaned the ICA controller last year during the summer.

Edited by 1-3-2-4, 20 January 2013 - 06:45 PM.


#4 afterbang

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Posted 20 January 2013 - 07:57 PM

This is just my experience but, my P0400 was solved by just replacing the BPT and the 3 small tubes that run to it. When I removed the EGR valve, there was very minimal carbon build-up and my 98 Outback has 190k on it.

Don't let anyone charge you $600 dollars to do that work on your Legacy. Clean yours out and if that doesn't solve it, grab a couple BPT valves out of some junkyard cars to try out. The actual EGR pipe could clogged too but you can clean that out yourself as well. It can be a pain to reinstall the EGR pipe but all of these jobs are fairly minimal.

Good Luck!

#5 1-3-2-4

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Posted 22 January 2013 - 10:51 AM

No doubt you found the location by now but here it is for others

Posted Image

Also I heard when the engine is cold the EGR should not open when revved until warmed up, correct?

Edited by 1-3-2-4, 22 January 2013 - 11:02 AM.


#6 ivans imports

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Posted 22 January 2013 - 11:07 AM

see that black and green transducer suck on the larger line to egr if whont hold vacume is toast. the digafram ruptures inside and it dosent work have had 6 in a row up here it gets water droplets in it and freezes and ruins the valve

#7 1-3-2-4

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Posted 22 January 2013 - 11:21 AM

I assume larger line (looks the same size to me) I'm guessing you mean the one on the right, I don't have a hand vacuum pump just a electric one, not sure how much vacuum I did to test with, I would suspect carbon buildup with almost 250k.

#8 1-3-2-4

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Posted 22 January 2013 - 12:46 PM



I was in a bit of a rush to drop someone off but from my testing car did not stall with the EGR open, forgot to test the EGR solenoid, for some reason I was thinking BPT :-/

All lines to and from BPT are as hard as I don't know what.. given that it's like 25F out right now it's a sure way for them to rip..


I might have to try this weekend to clean out the EGR.

Also it takes a bit of force to open the EGR as you can see in the video

#9 ivans imports

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Posted 27 January 2013 - 11:48 AM

the one strait of the bottom gos to the stainless line

#10 Fairtax4me

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Posted 27 January 2013 - 11:59 AM

At the beginning of the video when you rev the engine you can see the valve opening and closing on its own, so it's operating normally. Probably just clogged and not allowing exhaust through.

#11 ivans imports

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Posted 27 January 2013 - 12:06 PM

wow noisy motor valve addjustment the egr should stall the engine when you open it like that i still blame the transducer diafram it is trying but drops out

#12 1-3-2-4

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Posted 27 January 2013 - 03:05 PM

Too bad I don't have enough carb cleaner but I know as soon as I touch those lines they are going to split.. This Friday I will have a go at it hard to have free time around here.

#13 1-3-2-4

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Posted 27 January 2013 - 03:08 PM

wow noisy motor valve addjustment the egr should stall the engine when you open it like that i still blame the transducer diafram it is trying but drops out


It's not noisy at all... I'm right near the injectors.. the Injectors on Subarus are one of the loudest I've heard.. and given they are at almost 250k.

#14 1-3-2-4

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Posted 28 January 2013 - 09:54 AM

I just took the EGR off as soon as I got home

Posted Image

Posted Image

After on the EGR

Posted Image EGR holds pressure fine with just my finger or if I suck on the vac line end I can get it to move, also picked up 6ft of new hose more then enough so I can keep some as spare.

Now for the car end.. as it's snowing now taking the EGR off gets me better access to the EGR pipe but the lower one is a pain now.. Is it possible to get the lower one off with the engine in the car? I did it when mine was out..

For the port on the car same as I did inside with the carb cleaner? should I go easy on the carb cleaner where the EGR sits or do I just need to clean the EGR and just the pipe? I assume like the pipe it all leads down to the head and I don't want to go nuts.

Well looks like I should of made sure I had a gasket on hand.. Advance or auto zone don't have them here.. I hate dealing with them here since you wait in line for 10 min only to have them say they don't have it.. ordered it off Amazon and that's it.. I have a decent size vac leak now, anything I can use to seal to temporary? funny thing was the gasket was pretty thin.. thinner then most gaskets I've ever seen.

I don't think you can use RTV or anaerobic gasket because it's under vacuum right?

Edited by 1-3-2-4, 28 January 2013 - 12:36 PM.


#15 subienewbie111

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Posted 28 January 2013 - 02:35 PM

Thanks for the replies! Sorry it took a while to update. Fortunately I did get a second opinion and what do you know? No carbon buildup, just the transducer was faulty - so that part needed to be replaced. WAY less than that old $500-something quote I had, ridiculous. That price included an oil change and inspection but still - HECK no. Now the check engine light is back off, all is well, the old subie still keeps going and going and going and going ... Hope other people with the same issue are getting their problems solved!

(Of course, now I have to deal with my battery being 100 years old [not really, but...you get the idea] and the fact that it will probably die soon - that and the car occasionally overheats in very hot weather going uphill... but I don't have to deal with that just yet.)

#16 Fairtax4me

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Posted 28 January 2013 - 04:22 PM

The factory gasket is a stamped piece of stainless steel and Ive re-used those before with no trouble. If yours didn't survive just seal it up with some aluminum foil folded over a couple times. Works great and is resistant to the heat and exhaust gases. Cut the holes for the opening and the bolts out with an x-acto knife. Just be careful not to kink the foil up too much.

Clean as much crud as you can out of that intake manifold too.

#17 1-3-2-4

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Posted 28 January 2013 - 06:28 PM

I ended up just getting the gasket off Amazon, and I did clean as much as I could out of the intake manifold, and what was the size of the EGR pipe again?

#18 1-3-2-4

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Posted 29 January 2013 - 04:22 PM

So far no code I'm not sure if a drive cycle is starting up and car comes up to operation temp or just off/on.. but nevertheless 3 operating temp cycles and I don't see the code back..

Does not seem to hesitate when going up the ramp, which was evident of a misfire, idle seems smoother.. car still wont stall if I hold the EGR open if that matters or not.

#19 1-3-2-4

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Posted 31 January 2013 - 09:44 PM

still no code so it's done! :clap:

#20 Fairtax4me

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Posted 01 February 2013 - 01:24 PM

The port in the intake manifold may still be partially clogged. That's a PITA to clean though.

#21 1-3-2-4

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Posted 01 February 2013 - 02:41 PM

Well at least it's off :)




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